3D mensuration tools on Imagery tab are disabled

[EvanThoms]

I would like to measure the volumes of some features in the ESRI Terrain image service, which seems like it should be possible with the 3D mensuration tool 'Volume' on the Imagery tab, given what I have read about it. But the tools are disabled whether I set Elevation (in the Mensuration Options dialog) as the image service or a locally saved clip from it. What am I missing? 

[DanPatterson]

Mensuration Options—ArcGIS Pro | Documentation

and in the type of imagery

Image mensuration—ArcGIS Pro | Documentation

one would assume esri's Terrain service would have elevation

[BrianElliott1]

did you resolve this issue? i have same issue, Dan's response was no help....